Abstract
BackgroundStevia rebaudiana Bertoni has various pharmacological actions, which includes antidiabetic, antioxidant, anti-inflammatory activities. The superoxide and consequently NADPH oxidase (Nox) are relevant targets involved in biological effects of Stevia. The presence of NADPH-containing superoxide-producing lipoprotein (suprol) in Stevia leaves has not yet been tested. The mechanism of producing superoxide radicals (O2−) by suprol was determined in vitro, which is associated with the electron transfer from NADPH in the composition of suprol by traces of transition metal ions (Fe3+ or Cu2+) to molecular oxygen, turning it into O2−. It is expected that the therapeutic efficacy of Stevia leaves is caused by specific activity of superoxide-producing lipoprotein fraction.MethodsFor the first time, from the dry leaves of Stevia the NADPH-containing superoxide-producing lipoprotein was isolated and purified. The specific content of suprol (milligrams in 1 g of Stevia leaves- mg/g) was determined after desalination of suprol and lyophilization.ResultsAccording to the method provided, the specific content of the isolated suprol from Stevia’s leaves was up to 4.5 ± 0.2 mg / g (yields up to 68.5 ± 4.7%, p < 0.05, n = 6). Nox forms a stable complex with suprol. The optical absorption spectrum of the Nox-suprol complex represents the overlapping suprol and Nox spectra, with a certain background increase and characteristic features of optical absorption for Nox. Due to O2− producing capacity suprol-Nox complex discolors KMnO4 solutions, Coomassie brilliant blue, restores nitrotetrazolium blue to formazan and oxidizes epinephrine to adrenochrome. The oxidation activity of adrenaline is 50.3 ± 5.1 U / mg / ml (p < 0.05, n = 6).ConclusionSuperoxide-producing lipoprotein fraction-Nox complex from Stevia leaves (membranes) can modulate redox regulated signaling pathways and may play a positive role in type-2 diabetes by means of adrenaline oxidation mechanism.
Highlights
Stevia rebaudiana Bertoni has various pharmacological actions, which includes antidiabetic, antioxidant, anti-inflammatory activities
Steviol glycosides from the leaves of Stevia reduce the expression of genes of gluconeogenesis in the liver [9], increase the secretion and utilization of insulin, the sensitivity of cells to the effect of insulin on the experimental mouse model of insulin resistance caused by fructose [10], and reduce the level of oxidative stress of liver [11]
In our earlier studies in experimental model of type II diabetes caused by intensive consumption of dietary fructose we have shown that Stevia exhibits a membrane-stabilizing role of reducing increased level of total fractions of NADPH oxidase isoforms from central nervous system tissues and regulates NADPH-dependent O2−-producing activity [15]
Summary
Stevia rebaudiana Bertoni has various pharmacological actions, which includes antidiabetic, antioxidant, anti-inflammatory activities. The presence of NADPH-containing superoxide-producing lipoprotein (suprol) in Stevia leaves has not yet been tested. Stevia rebaudiana Bertoni is a plant species in the genus Stevia of the sunflower family (Asteraceae), commonly known as candy leaf, sweet leaf, or sugar leaf. There are more than 100 species of stevia plant belonging to family Asteraceae, but Stevia rebaudiana Bertoni stands out for NADPH in the composition of suprol by traces of transition metal ions (Fe3+ or Cu2+) to molecular oxygen, turning it into O2− [3]. In our earlier studies in experimental model of type II diabetes caused by intensive consumption of dietary fructose we have shown that Stevia exhibits a membrane-stabilizing role of reducing increased level of total fractions of NADPH oxidase isoforms from central nervous system tissues and regulates NADPH-dependent O2−-producing activity [15]. It is expected that efficacy of Stevia leaves is conditioned by specific activity of superoxide-producing lipoprotein fraction
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